Latex activator



Patented July 23, 1946 j f UNITED; fsT'ArEs corporation of Ohio,

N6 Drawing." Application August- 11, 1045;] 1

Serial No. 610,398

3 Claims.

2 oxide. The accelerator used with the black was tetraethanol ammonium Captax solution (24.4 per cent Captax). The black was a reinforcing black added as a 40 per cent dispersion. The l-atex'was 60 per cent solids. The amounts are parts by weight.

A B O D E F G B.

Latex, 60% 167 167 167 167 167 167 167 167 1 Black, 40% 93. 95 93. 95

Zinc oxide, 50% 5 5 5 5 04, 507 l3. 7 l3. 7 l3. 7 13. 7

Sulfur, 50% 4 4 4 4 4 4 4 4 Ammonium Captax (27.5% Captax)-. 2. 73 3. 64 4. 55 2.73 3. 64 4. 55

T. E. A. Oaptax (24.5% Oaptax) 3.07 3. 07

pounds which are suitable include the sodium,

amomnium, etc., salts, benzothiazyl disulfide, cyclohexyl benzothiazyl sulfenamide, etc.

It has been realized that zinc oxide is not altogether satisfactory for compounding with latex because it renders the latex unstable. The zinc oxide cannot be omitted from latex without replacing it with some activator. According to this invention it is replaced entirely or largely by red lead oxide (Pb304).

In compounding latex with red lead for cornparison with latex compounded with zinc oxide, it has been assumed that the activation is due to the metal, and equivalent proportions of the two metals are used in the following formulae.

The comparison recorded below was made with 5 parts of zinc oxide and 13.7 parts of red lead The zinc-oxide-containing compound was fluid and stable for only about 10 minutes, and the test slabs, therefore, had to be cast in a hurry. The lead-oxide-containing compound was thin and so stable it could be stored for days with very little change in stability. The activator was dispersed by ball-milling with 4 per cent of Darvan (a dispersing agent) before adding to the latex. The particles of lead oxide and zinc oxide in dispersed form were about the same size.

Pure gum compounds containing red lead oxide are an intense orange color which turns to black on curing,

Test slabs were obtained by drying the latex on glass plates. All slabs were dried one week at room temperature in the open and then one week in the dessicator. Below are recorded the results of tests on the physical properties of samples press-cured at 275 F. for 20, 40, 60, and 80 minutes, respectively, as indicated. The amount of accelerator'figured as Captax is given to make the table most informative.

Formula A B o D E F G 11 Gupta-x Pure gum compounds Black compounds Cure Zinc oxide Red lead oxide ZnO PbgO;

3 73 3s 73 73 3s 73 5 9 50 730 730 700 750 770 720 500 025 30 750 770 725 750 755 720 530 570 -33 33 ii? ii 53 i2? 183 3 4 5 420 200% maul 85 150 125 100 130 100 500 405 80 80 150 150 100 150 100 580 475 3 32 22a 3 30 73 50 400% 50 250 330 300 250 275 200 11370 1; 200 80 250 300 325 300 300 4 230 1,440 1,400 a. 3 13: 1020 .3 1 32 600% modulus 60 :0 0 1:120 '970 1:425 1:375 1: "5356' 3:220 1, 030 025 1, 1, 500 1, 410 1, 290 3, 515 20 2,790 3,135 3,130 4,000 4,030 3,525 ,550 3,985 Tensile 40 3, 050 3, 350 3, 850 3, 550 4, 220 3, 725 3, 3, 470

' 1,. Ernst, Schmidt, Akron, Ohio, assignor to The Firestone Tire & Rubber Company, Akron, Ohio, a

other compolmding; ingredients maybe uti-1 lized. Fillers", etc.,may= be added. The latex used. need not be concentrated. Other compounding ingredients than those specified may be employed; Modifications are permissible within the scope qt 5; 1 p the appended claims.

What I claim is:

V 1. Latex containing sulfur, a benzothiazyl 'ac- I celerator, substantially free of zinc xideand containing red lead oxide in an amountsufiicierrttq i0.

activate the accelerator.

the accelerator.

3, The process of vulcanizing latex rubber which comprises, Yul'canizing with sulfur and a bcnzothiazyl accelerator in' the presence of red lead oxide as an activator.

ERNST SCHMIDT. 

